Leaders of Thailand's pro-establishment "Yellow Shirts" huddled Monday to plot their next move against rival "Red Shirts" who are bracing for a crackdown on their Bangkok protest base, AFP reported.

The Yellows have warned they will take action to "protect the country" if authorities do not deal with the anti-government Reds who are defying a state of emergency with their mass rally in the heart of the capital.

A one-week deadline set by the Yellows for an end to the crippling protests expired with no end in sight to the tense standoff, which has twice descended into bloodshed this month, leaving 26 people dead and hundreds injured.

Prime Minister Abhisit Vejjajiva has rejected an offer by the Reds, who mostly support former premier Thaksin Shinawatra, to disperse if elections are held in three months' time -- softening earlier demands for snap polls.

Appearing on national television Sunday alongside his army chief, Abhisit vowed to retake the sprawling protest site that has paralysed Bangkok's main retail district, but gave no indication of when a crackdown might come.

Thailand is largely split between the mainly rural poor and urban working class Reds, and the Yellows who staged their own street protests that heralded a 2006 coup ousting their enemy Thaksin.

Yellow protesters in 2008 blockaded Bangkok's two main airports, before a controversial court verdict removed Thaksin's allies and allowed a parliamentary vote that brought in the current government.

The Yellows had remained largely silent since the Reds began mass rallies in mid-March demanding immediate elections, but there are now growing fears of clashes between the rival groups.

A tense standoff between the Red Shirts and pro-government crowds ended with fresh blood spilled on the streets last Thursday when grenade attacks left one woman dead and scores wounded.

The red-clad movement remained as defiant as ever Monday as another night passed with no sign of a crackdown on their base, which has been fortified with barricades made from piles of truck tyres and sharpened bamboo poles.

"If Abhisit fails to crack down on us, he will have to leave office," said one of the Reds' leaders, Nattawut Saikuar.

If he succeeds in forcing them out, the Reds will rally across the country and prepare for a return to the capital, he said.

When troops tried to sweep the Reds out of Bangkok's historic area on April 10 they suffered a humiliating retreat as deadly street clashes left 25 people dead and hundreds injured in the worst civil violence in almost two decades.

The military has warned protesters would face live weapons fire in any new clashes.

Hopes for an agreement to end the long-running protests were dashed Saturday when Abhisit ruled out an offer by the Red Shirts to disperse if parliament were dissolved in 30 days for elections in three months' time.

In the latest violence in the capital, 11 people, including three policemen, were injured in a grenade attack late Sunday on the house of former prime minister Banharn Silpa-archa, police said.

Another grenade attack targeted a regional police station in northern Chiang Mai province late Sunday but nobody was hurt.

Ramping up the pressure on Abhisit, the Election Commission has called for his ruling Democrat Party to be abolished over allegations of an illegal political donation in 2005 and misuse of a commission grant.

The first count will be forwarded to the Attorney General, who has 30 days to consider it. The election body has until Monday to forward the second case directly to the constitutional court.